Fibroblast Growth Factor Receptors
Fibroblast Growth Factor ligands (FGFs) constitute a family of over twenty structurally related polypeptides that are developmentally regulated and expressed in a wide variety of tissues. FGFs stimulate proliferation, cell migration and differentiation and play a major role in skeletal and limb development, wound healing, tissue repair, hematopoiesis, angiogenesis, and tumorigenesis (reviewed in Ornitz and Itoh, 2001).
The biological action of FGFs is mediated by specific cell surface receptors belonging to the receptor protein tyrosine kinase (RPTK) family of protein kinases. These proteins consist of an extracellular ligand binding domain, a single transmembrane domain and an intracellular tyrosine kinase domain that undergoes phosphorylation upon binding of FGF. The FGF receptor (FGFR) extracellular region contains three immunoglobulin-like (Ig-like) domains (D1, D2 and D3), an acidic box, and a heparin-binding domain. Five FGFR genes encoding for multiple receptor variants have been identified to date. Alternative splicing further increases the diversity of the FGFR family. The second half of the third Ig-like domain in FGFR1, 2 and 3 is encoded by one of two exons, IIIb or IIIc, generating receptors with different ligand affinities and specificities.
Fibroblast Growth Factor Receptors and Malignancy
Certain FGFRs have been implicated in certain malignancies and proliferative diseases. FGFR3 is the most frequently mutated oncogene in transitional cell carcinoma (TCC) of the bladder where it is mutated in more than 30% of the cases (Cappellen 1999). Yee et al. (2000) identified a mutation in FGFR3 linked to cervical carcinoma. van Rhijn et al. (2002) disclosed FGFR3 mutations in bladder cancer which were previously identified in skeletal disorders.
FGFR3 mutations seem to have a central role in the early development of papillary bladder tumors and can serve as a target for treatment (Billerey et al., 2001; Cappellen et al., 1999). These tumors follow a common molecular pathway, which is different from tumors with concomitant carcinoma in situ (CIS). However, FGFR3 mutations do not seem to play a role in bladder cancer progression (Zieger, et al., 2005).
FGFR2 mRNAs were found to be overexpressed in both human pancreatic cancer cells and the adjacent pancreatic parenchyma (Ishiwata et al., 1998,) and Kurban et al., (2004) identified FGFR IIIb (KGFR) expression in cervical cancer cells. Lorenzi et al. (1996) have identifies a constitutively active form of FGFR2 in rat osteosarcoma cells.
In general, FGFR2 exhibits expression of the IIIb isoform in epithelial type tissues and the uroepithelium and the IIIc isoform in the mesenchyme. FGFR2 subtype IIIb (FGFR2-IIIb) was shown to have tumor suppressive properties, i.e. be downregulated in a subset of transitional cell carcinomas of the bladder (Bernard-Pierrot et al., 2004; Ricol et al. 1999).
Johnston et al. (1995) reported that FGFR4 and FGFR2 are expressed at higher levels in breast cancer cell lines than in normal epithelial cells. Khnykin D et al. (2006) found that in the majority of cases FGF2-FGFR4, but not FGFR1, were expressed by malignant cells. FGFR4 was shown to be associated with pituitary tumors (Ezzat, et al, 2002) and breast cancer progression (Bange, et al., 2002).
Recent findings implicate that single nucleotide polymorphisms (SNPs) in FGFR2 were highly associated with breast cancer (Hunter et al., 2007). An additional study demonstrated that SNPs in five novel independent loci including FGFR2 exhibited strong and consistent evidence of association with breast cancer (Easton et al., 2007).
These and other findings implicate the involvement of both FGFR2 and FGFR3 in the pathogenesis of various malignancies rendering these FGF receptors potential targets for therapeutic intervention in these cell proliferative diseases.
Fibroblast Growth Factor Receptor Inhibitors
International Patent Publication WO 03/024987 discloses antisense compounds useful for modulating FGFR2. International Patent Publication WO 03/023004 discloses antisense compounds useful for modulating FGFR3. U.S. Pat. No. 6,900,053 teaches compositions comprising antisense oligo-nucleotides and methods for modulating the expression of FGFR2. Those compositions were found useful in the treatment of diseases associated with overexpression of FGFR2. Small molecule tyrosine kinase inhibitors, which have been shown to inhibit the activity of certain tyrosine kinase receptors, are disclosed in U.S. Pat. Nos. 6,987,113; 6,683,082 and others.
International Patent Publication WO 02/102972, co-assigned to the assignee of the present invention and incorporated by reference herein, discloses antibodies to receptor protein tyrosine kinases, specifically anti-fibroblast growth factor receptor 3 (FGFR3) antibodies. Certain antibodies shown to be specific for FGFR3 neutralize FGFR3 activity and are potentially useful for treating skeletal dysplasias such as achondroplasia and proliferative diseases such as multiple myeloma. That disclosure notes bladder cancer in a list of proliferative diseases in which FGFR3 is known to be involved but does not teach the method of treating or attenuating bladder cancer using an anti-FGFR2 antibody.
PCT Publication WO 2006/048877, co-assigned to the assignee of the present invention teaches a method of treating multiple myeloma comprising administering to an individual in need thereof an anti-FGFR3 antibody which is specific for wild type FGFR3.
PCT Publication WO 2004/110487 assigned to the assignee of the present invention, provides a method of treating a T cell mediated disease comprising administering to a subject in need thereof an FGFR3 antagonist.
International Patent Publication WO 2005/066211 teaches antibodies directed to FGFR polypeptides, and methods of use thereof for treating tumors. That application provides tables disclosing human tumors, which express the various FGFR proteins but there is no teaching of cross reactive antibodies. Martínez-Torrecuadrada et al. (2005) teach anti-FGFR3 antibodies which inhibit bladder carcinoma cell proliferation.
Kan et al. (1993) disclose that heparin interacts with a specific region in the extracellular domain of the FGFR, and is essential for FGFR activation. They synthesized a peptide corresponding to the heparin binding domain of FGFR1 and raised polyclonal antibodies specific to this peptide. Both the peptide and the antibodies were antagonistic to FGF1-stimulated cell growth. However, Kan et al. did not demonstrate blocking of other FGF receptors nor do they show inhibition of constitutive receptor activation.
Fortin et al. (2005) used antibodies specific to a single receptor subtype, namely either FGFR1, FGFR2 or FGFR3 to examine FGF/FGFR interactions during oligodendrocyte development. In this article there is no teaching of an antibody that binds both FGFR2 and FGFR3 with high affinity.
Nowhere in the art is it suggested that anti-FGFR antibodies cross-reactive with more than one receptor subtype would be particularly useful for treating neoplasms. Nowhere in the prior art was it taught or suggested that antibodies capable of blocking heparin binding to the heparin binding site of an FGF receptor could exhibit cross-reactivity to multiple receptor subtypes. Thus, there is an unmet need for anti-FGFR antibodies capable of blocking both ligand-dependent and aberrant constitutive ligand-independent FGF receptor activation, thereby modulating various biological abnormalities.